The president is currently deciding whether to decertify the Iran nuclear deal brokered by the Obama administration. Defense Secretary James Mattis, among others, has said decertifying the deal is not in U.S. security interests.

The administration is also pushing for the denuclearization of North Korea, aiming to deter the dictatorship's nuclear and missile programs with economic sanctions. Trump has made defiant warnings to Pyongyang, including a threat of "fire and fury."

In comments before the meeting, Trump referenced Iran, North Korea, Afghanistan and the terror group ISIS. Trump said "we must not allow Iran to obtain nuclear weapons," adding that the country has "not lived up to the spirit of their agreement."

On North Korea, the president said "we will do what we must do" to prevent Pyongyang from threatening the U.S. and its allies.

"And it will be done, if necessary — believe me," he added.

Trump said he expects the leaders to provide him with a "broad range of military options, when needed, at a much faster pace."